I] FERTILIZERS 13 



10 grams of the sample with strong sulphuric acid and ignite in a muffle at a low red 

 heat to destroy organic matter. Add a little strong hydrochloric acid, warm slightly 

 in order to loosen the mass rom the dish, transfer to a 250 cc. graduated flask, add 

 ammonia and ammonium oxalate and proceed as in (a). 



42 DETERMINATION. 



(a) Mixed fertilizers. — Evaporate 50 cc. of the solution in 41 (a) nearly to dryness, 

 add 1 cc. of dilute sulphuric acid (1 to 1), evaporate to dryness, and ignite to white- 

 ness. Maintain a full red heat until the residue is perfectly white. Dissolve the 

 residue in hot water, using at least 20 cc. for each decigram of potassium oxid pres- 

 ent, add a few drops of hydrochloric acid, and platinum solution in excess. Evap- 

 orate on a water bath to a thick paste. Treat the residue with 80% alcohol, avoid- 

 ing exposure to ammonia. Filter, wash the precipitate thoroughly with 80% alco- 

 hol both by decantation and on the filter, continuing the washing after the filtrate 

 is colorless. Then wash with 10 cc. of the ammonium chlorid solution to remove 

 impurities from the precipitate and repeat 5 or 6 times. Wash again thoroughly 

 with 80% alcohol and dry the precipitate for 30 minutes at lOO'C. Weigh and cal- 

 culate to potassium oxid. The precipitate should be perfectly soluble in water. 



(b) Muriate of potash. — Acidify 50 cc. of the solution prepared according to 41 

 (b) with a few drops of hydrochloric acid, add 10 cc. of platinum solution and evapo- 

 rate to a thick paste. Treat the residue as under (a). 



(C) Sulphate of potash; sulphate of potash and magnesia; andkainit. — Acidify 

 50 cc. of the solution prepared according to 41 (b) with a few drops of hydrochloric 

 acid and add 15 cc. of platinum solution. Evaporate the mixture and proceed as 

 directed under (a), except that 25 cc. portions of the ammonium chlorid solution 

 should be used. 



(d) Water-soluble potash in wood ashes and cotton hull ashes. — Prepare the solution 

 according to 41 (a) and proceed as directed under (a), paying special attention to 

 the last sentence. 



Method II.— Official. 

 (The Lindo-Gladding method is preferable in the presence of soluble sulphates.) 



43 REAGENTS. 



Described under 40. 



44 PREPARATION OF SOLUTION. 



Prepare the solution as directed under 41, omitting in all cases the addition of 

 ammonium hydroxid and ammonium oxalate. 



DETERMINATION. 



45 



Dilute 25 cc. of the solution made as directed under 44 (50 cc. if less than 10% 

 of potassium oxid be present) to 150 cc, heat to 100°C., and add, drop by drop, with 

 constant stirring, a slight excess of barium chlorid solution. Without filtering, add 

 in the same manner barium hydroxid solution in slight excess. Filter while hot and 

 wash until the precipitate is free from chlorin. Add to the filtrate 1 cc. of strong 

 ammonium hydroxid, and then a saturated solution of ammonium carbonate until 

 the excess of barium is precipitated. Heat and add, in fine powder, 0.5 gram of 

 pure oxalic acid or 0.75 gram of ammonium oxalate. Filter, wash free from chlorin, 

 evaporate the filtrate to di'yness in a platinum dish, and ignite carefully over the free 



